Paper sizing

ABSTRACT

A paper sizing agent which contains as an active sizing component at least one N,N&#39;&#39;-alkyl-substituted aspartimide in which at least one and preferably two of the alkyl substituents consists essentially of a straight or branched alkyl chain of at least 16 carbon atoms. This aspartimide component is useful for both internal sizing or surface sizing of paper, especially paper formed of cellulosic fibers, and is readily applied as an aqueous emulsion, for example with an emulsifying agent and/or a protective colloid.

United States Patent [191 and/or a protective colloid.

Beck Aug. 19, 1975 l PAPER SIZING Primar Examinei'Theodore Morris [75 lnventor: Heinz Beck, Nicleggener, Germany Z s g F On, Kell, Thompson ur e [73] Assignee: Akzo N.V., Arnhem, Netherlands 221 Filed: Apr. 1, 1974 57 ABSTRACT [2 l Appl No: 456,614 A paper sizing agent which contains as an active sizing component at least one N,N-all yl-substituted asparti- Foreign Application Priority Data mide 1n which at least one and preferably two of the 7 alkyl substituents consists essentially of a stralght or 1973 Germany 2318894 branched alkyl chain of at least 16 carbon atoms. This g aspartimide component is useful for both internal siz- [52] US. (,l. 106/213; 117/156; 162/158, ing or surface Sizing of paper especially paper formed 162/175 of cellulosic fibers, and is readily applied as an aqueig 'ld 'f' Cosh l gl glg igz /z s s ous emulsion, for example with an emulsifying agent 6 ie 0 care 260/3265 F, 326.5 FM; 117/156 12 Claims, N0 Drawings PAPER SIZING In addition to colophony (rosin), a number of other compounds have been used in the paper industry as sizing agents, including by way of example such compounds as fatty acids, fatty acid anhydrides, fatty-am-- ides, diketenes and the like. Compounds which contain acid groups precipitate as aluminum salts onto the paper fibers in the sizing procedure, for example, where aluminum is commonly present in the aqueous sizing solution as when using aluminum sulfate (alum) as a retention agent in an amount of about 0.5 to 3.0%

and preferablyabout 1.0 to -2.0%-by weight based on,

the paper fibers. The sizing then succeeds-only at a relatively low pl-l-va'lue, and these sizing agents containing acid groups therefore have a poor resistance to aging.

Also, the' amount of 'such'sizi'ng agentsis relatively high,

usually about 1.5 to 3% by weight with'i'eference tothe Agents with an ac lating or'a'cid-reacting' effect, such as fatty acid anhydrids oralk'yl lietene dimers,are also disadvantageous becau se'of their limited stability. They"- react not only'with the hydroxyl groups 'of c'ellulosic materials but 'also with all" other-nucleophilic sub:v

stances including water. [for this'reasonfthese sizing agents should not be added eitlierat high pH-values'or in the presence of aluminum sulfate at low pHvalues.

For a more" detailed discussion of synthetic sizing agents, attention is directed to Pulp and Paper Manufacture edited: by lVlac Donald 'and Franklin," Second Edition, Vo in, eor' w iiin Boek'cempe'n N.Y.

( 9 surface treatments, including surface sizing,"oii pages 71-77, as well as internal sizing on pages 35 50. The

papermaking process is generally disclosed by this reference together with suitable apparatus, including that which may be used for sizing operations. This edition I is therefore incorporated hereby by reference as fully as if set forth in its entirety.

One object of the present invention is to provide a synthetic paper size or sizing agent, especially for cellulosic fibers, which overcomes the inadequacies and disadvantagesofthe previously usedpaper sizes Another object of .th'e invention 'is to provide improved paper sizing compositions and procedures capable of providing better sizing effects and/0r more widely applicable sizing methods. These. and .other objects and advan tagesof the: invention will becomeinoi'e apparent upon consideration of the following detailed specification.

pp. same reference alsodiscusses eep-7; a

which may be present once or twice, the aspartimide compounds of the invention may contain a total of about 18 to 104 carbon atoms, preferably about 40 to 8O carbon atoms, in the alkyl chain or chains. Although the alkyl chain is preferably a straight chain of essentially saturated hydrocarbon structure, it may be a branched chain and it may also be interrupted by one or two hetero atoms such as nitrogen, oxygen or sulfur v The alkylchain may also contain one or two functional groups, especially al primary, secondary or tertiary amino group. Other functional groups include hydroxyl, ether, ester, carboxyl or carbonyl groups. Als'o included are sulfur-derivatives such as thioether, thioester and sulfonic or sulfonyl groups. The presence of one or two such hetero atoms or functional-groups in the alkyl chain or chains can be tolerated without departing substantially from the essential hydrocarbon structure of these chains and without impairing the aspartimidet'compounds."

paper sizing properties of the N,N'-alkyl-substituted The intentionalinclusion of such heteroiatoms and especially the functional groups is of particular advan tage' for the purpose of providing especially compatible compositions for paper treatment where similar long chain alkyl-substituted compounds may be used as surface active agents in the sizing operation or in previous or subsequent treatments of the paper. Moreover, minor variations in the properties of. the .sized paper can be achieved with an otherwise closely related class of sizing agents based upon the essential disubstituted aspartimide structure.

A single generic structural formula cannot be given which will include a=-number-;of.-suitable variations of the aspartimide compounds, and, in some instances it is easier to' provide a mixture of these sizing agents rather thana single compound.;.

However, the -N,N'-.alkylesubstituted aspartimides of the present invention, sometimes referred to as. as-. paraginimides may be generally illustrated .by. the

structural formula cH c wherein R and R eachpreferably represent a long chain'alkylv group of} at least 16 andpre ferably about 18 to 24 carbon atoms. lt isjalso feasible however, to pro; vide somewhat more complex tertiary amino cornpounds represented by the formula i i i i "YLIH 0? e a V wherein R and R have 'the same meaning givenabove while R is hydrogen, R or another radical with R and R again having the same meaning given above.

Two succinimido groups may also be joined by an alkylene bridge between the imido nitrogen atom as represented by the formula where R" is hydrogen or R and m is an integer of 2 up to about 8, preferably 3 to 6, and R is again a long chain alkyl group.

Still another representative class of aspartimide compounds may be illustrated by the formula wherein R is the long chain-alkyl group and m is an integer of 2 to 8, preferably 3 to 6.

'In all of the noted formulae, it will be understood that the alkyl chain may contain hetero atoms and/or functionalgroups as described above, i.e., so that R, and R may be further defined as being long chain radicals of the formulae R. CH J R4 in which:

n is a whole integer of at least 2,

R is hydrogen alkyl, alkoxy, alkoxyalkyl, hydroxy, hydroxyalkyl, hydroxyalkoxyalkyl, thioalkoxy, alkanoyl, alkoxycarbonyl, and alkylcarboxamido or alkylamidocarbonyl; and

R and R each represent hydrogen, alkyl, hydroxyalkyl, alkoxyalkyl or alkyl substituted by a terminal carboxylic acid or its alkyl ester, provided however that each long chain radical must contain a total of at least 16 carbon atoms and preferably about 18 up to 40 carbon atoms.

Thus, in addition to the preferred hetero atoms N, O-- and -S as bridging groups, these long chain radicals may also contain other functional bridging groups such as or the methylene bridge in which Y is hydrogen, alkyl, hydroxy or even other functional substituents which are essentially inert under a wide range of sizing conditions and up to temperatures of about 200C.

In general, it is preferable to employ those long chain radicals which are derived from readily available aliphatic amines, especially saturated fatty amines, butu also diamines and polyalkylpolyamines.

The N,N'-alkyl-substituted aspartimides can be easily obtained by melting together at least one amine and maleic acid anhydride or the lower alkyl esters of maleic or fumaric acid, followed by heating for a short period of time, e.g., up to one hour, at a temperature of about C. to 200C. in general, the reaction product may be used directly in its crude form without purification, or it may be recrystallized from a suitable solvent such as acetone.

By way of example, the following types of amines can be identified as being especially suitable for the preparation of the desired aspartimide compounds. Where the compound is defined by a number, this is its Registry No. see Chemical Abstracts lndex, 1967-1971, Vols. '66-75.

1. Alkylamines, for example:

Hexadecylamine Qctadecylamine Eicosylamine Docosylamine Tetracosylaminoe (These amines or their mixtures are commercially available.) 2. Alkylamines containing an imino (Nl-l) bridge in the carbon chain, for example compounds of the formula R-NH(CH ),,NH (v) wherein a is a small whole integer of about 2 to 6, preferably 2 or 3, R preferably being an alkyl chain of i4 29 to C24H49' 3. Alkylamines containing a tertiary nitrogen atom in the chain, for example compounds of the formula:

R N-wHm- (v1) wherein a has the meaning previously given and R is preferably an alkyl chain of about C H to C I-I Examples of such compounds are:

N,N-ditetradecylethylenediaminel ,2 N,N-dihexadecylpropylenediamine-l ,3 N,N-dioctadecylpropylenediamine-1 ,3 N,N-dioctylhexamethylenediamine-1 ,6

4. Amines with an oxygen (O) bridge in the carbon chain of the formula 2 or 3, and R is again preferably C I-1 to C H Examples of such compounds arcx Dodecylthiopropylamine (No. 2g873-33-4) Tctradecyllhiopropylamine (N0. 2g873-32-3) 6. Amines containing an ester group in the carbon chain, for example of the formula wherein a is again a small whole integer of about 2 to 6, preferably 2 or 3, and R is alkyl of about C H to C 11 preferably C H to C I-I Examples of such compounds are:

7. Amines with an amide group in the carbon chain,as represented by the formula wherein a has the meaning previously given and R is an alkyl chain of about C H 17 to C H preferably C I-1 to C I- Examples of these compounds are:

8. Amines which carry hydroxy groups on the carbon chain, for example:

9- or IO-hydroxyoctadecylamine 2,712,558) 4-amino-2-methyl-eicosanol (No. 19698-17-0) l-amino-9-octadecanol (No. 19698-16-9) l-amino-2,6,l0,l4-tetramethyl-pentadecan01-2 (No.

27885-72-9). 9. Amines which carry acid or ester groups on the carbon chain, .for example:

(See U.S.

22-amino-docosa'noic acid (No. 27306-09-8) 12-amino-stearic acid (No. 30616-18-3) 2-amino-2,6, 10, l4-tetramethyl-pentadecanoic or IO-amiho-stearic acid methyl ester (No. 29156-48-7) o-amino-stearic acid methyl ester (No. 30616-17-2) All of the above-noted amines represent suitable starting materials provided that there is at least one and preferably two long chains of at least 16 carbon atoms associated with one to two of the suc cinimido rings. However, where at least one or two of the R or R substituents represents a chain of at least 16 carbon atoms, one may also employ lower alkylamines, alkyldiamines or polyalkylenepolyamines having less than 16 carbon atoms, e.g. from from 2 to 10 and preferably 2 to 6 carbon atoms, such as ethylene diamine, hexylamine, hexamethylenediamine, dipropylenetriamine or the like. The lower alkylene diamines are of particular value in forming the bridging group (CH in formulae III, IV above. Such variations are possible because the initial acid reactant, e.g., maleic acid anhydride, can'first be reacted at a relatively low temperature, e.g,, up to C, to form an amide using one monoor diamine reactant acid followed by addition of another monoor diamine reactant and heatingfat the higher recommended temperature of about C to 200C to make the addition of the amine group-to the double bond and to close the imide ring.

C-CH

NR, O and CO, where R is alkyl which may also extend up to 26 carbon atoms or more. Two or more of these-bridges may be combined to yield the amide and-ester groups NHCO or CONH and OCO or COO as indicated above. Other minor variations such as the presence of one or two hydroxyl substituents or a number of lower alkyl substituents are also preferred.

Once the aspartimide compounds have been prepared, they are preferably made up in the form of aqueous emulsions for application as a paper sizing agent. Such emulsions are best produced by thorough mixing with the addition of an emulsifying agent or other components which ensure a uniform stable emulsion suitable for the treatment of paper. The emulsification of the aspartimide can thus take place in the presence of one or more of the following components:

a. An inorganic or organic acid, e.g., hydrochloric, sulfuric -.or phosphoric acids, or acetic, propionic or butanoic acids or longer chain alkanoic acids;

b. Cationic or nonionic emulsifiers or surface active agents of a wide variety known to be useful in paper sizing compositions and readily selected from any standard reference, e.g. quaternary alkyl ammonium chlorides such as hexadecylor octadecyltrimethyl ammo nium chloride or the oxyethylated and/or oxypropylated polyalkylenepolyamines; and

c. Other sizing components including protective colloids, usually in the form of watersoluble or waterdispersible polymers, such as gelatin, sodium alginate, carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), or a degraded or cationic starch preparation.

Other preferred-combinations of the paper sizing aspartimide compounds of the invention are those aqueous compositions which may further include one or more of the following components:

d. Alum, the common designation for aluminum sulfate, preferably of a good commercial grade which is low in iron content; this substance being particularly useful as a complexing agent in the sizing liquor;

e. Rosin, which consists primarily of abietic acid or closely related acids, preferably in smaller amounts as a fortified sizing agent, i.e., as compared to where rosin may be used alone, especially for internal sizing; with the aspartimide sizing agent, rosin can be added in preferred smaller amounts of 0.01 up to 1%, preferably about 0.1 to 0.5%, based on the fibrous content of the paper being sized;

f. Sodium aluminate (Na Al O as an extender of aluminum sulfate;

g. Wet-end additives such as polyacrylamides may also be included in small amounts;

h. Coloring agents, i.e., any compatible dyes or pigments useful for imparting color to the paper; and

i. Fillers and special fibers of all types, especially cheap materials such as calcium carbonate.

It is of particular value that one can achieve very good results in paper sizing with relatively smallamounts of the aspartimide sizing agent after it has been; emulsified,-preferably with a cationic emulsifier z lnd then diluted to form a sizing liquor. ln general, it is sufficient to add less than. 1.5% by weight of theaspartimide sizing agent with reference to the fibrous content of the paper' and very good results with internal or,surface sizing can be achieved in amounts of about 0.l to 1% by weight, preferably 0.2 to 0.8% by weight,,again with reference to the dry weight of the fibers in the paper. When used in combination with rosin or other sizing agents, one can use even smaller amounts of the aspartimide while also substantially reducing the required amount of the more conventional sizing agent.

It is especially surprising that the N,N-dialkylsubstituted aspartimides of the invention provide good sizing properties because other aspartic acid derivatives with similar structures exhibit no sizing activity at all or only an inconsequential sizing effect. Thus, very good sizing is obtained with N,N'-dioctadecylaspartimide while a similar compound, N-octadecylaspartic acid dioctadecyl ester exhibits no sizing activity at all. Also, melts of dioctadecylamine and maleic acid anhydride, which react without formation of the imide ring, develop only a very incomplete and unsatisfactory sizing effect.

A special advantage of the invention also resides in the fact that the aspartimide sizing agents are much more stable than the acid-forming agents. The sizing compositions can therefore be prepared as concentrates or as diluted liquors which are very stable in storage and in a wide variety of useful sizing compositions and under a wide range of sizing conditions. For example, the new sizing compositions in which the N,N'- disubstituted aspartimide is the active sizing component can be utilized in much wider pH ranges.

By comparison to rosin sizing agents, fatty acids or their anhydrides or fatty amides, the required amounts of the N,N'-disubstituted aspartimide compounds of the present invention are considerably smaller. Thus, as a general rule, it is sufficient and especially preferred to use these aspartimides in an amount of about 0.3 0.7% by weight for internal sizing and about 0.2 to 0.4% by weight for surface sizing, the percentages being with reference to the fibrous content of the paper.

The fact that these aspartimides can be applied at higher pH-values, for example at a pH of about 4.5 or more, preferably above 6, for example about'o to 9, is of particular value in producing papers having a very good resistance to aging.

Finally, the new sizing material and the methods of application permissible therewith offer a coemployment of very inexpensive fillers such as calcium carbonate or other additives, something which cannot ordinarily be achieved with some other known natural or synthetic sizing agents.

The use of specific sizing compositions and the method of applying them to a cellulosic paper are illustrated in the following specific examples. The values given for ink resistance were determined with the aid of a Hercules sizing tester, explained in Hercules Bulletin PM515, using the ink test according to German Industrial Standard DlN 53 126. The time in seconds was measured up to a remission of For the Cobb-test, there was used water at 20C. with a treatment time of one minute. The Cobb value was determined accordingto the method described in TAPPI Monograph, Series No. 33 (1971), pages l08l 14.

The following examples are illustrative only and are not intended as restrictions on the use of the paper sizing agent of the invention.

EXAMPLE 1 580 grams of N,N-dioctadecylpropylenediaminel ,3 and 86 gramsof maleic acid diethyl ester were heated for one-half hour at 200C, ethanol being distilled off.

9, There .were formed a light colored, pasty substance which woosa dioctadeeylaminopropyl)-aspartimide as, :the desired sizing agent. lt has the formula H 100 grams of this substance were mel ted, heated up to about 100C. and admixed under intensive stirring with a solution of grams of Arqua d, 1.6/50 in 880:

grarnsof water, (The Arquad .16/50 composition is a trademarked product obtained from Armour & Hess Ltd. and .is a biodegradable cationic emulsifier consisting-of a 50%fsolution of hexadecyltrimetliylammonium chloride in isopropanol), The resulting emulsion was sent through a flask hoinogenizer while hot at about 300 atm. gauge. From this original emulsion, an aqueous sizing. liquor was produced which contained 4%i' by weight of de raded starch in addition to 0.3% by weight of the active sizing agent.

A neutral paperof 70 glrn' in.,weigl'it per unit area was selected for sizing,- the paper being produced from 70%.coniferous cellulose sulfite pulp and 30%i'beech wood cellulose Sulfitepulp and 40 SR (the Schopper Riegler degree of freene ss of the pulp). This paper was surface sized on a conventional sizing press with the sizing liquor with an approximately 100% by weight absorption of the liquor by the paper. Accordingly, the sized paper contained about 0.3% by weight of the active sizing substance besides the starch, taken with reference to the cellulosic fibers. The sized paper, after drying, exhibited an ink resistance of 1.949 sec. and a Cobb value of 21.4.

EXAMPLE 2 The aspartimide obtained in Example 1 was again made up into an emulsion in the same manner except that the solution added to make up the original emulsion contained 20 grams of a cationic starch. The surface sizing was carried out exactly as in Example 1 and resulted in a paper with an ink resistance of 1.726 sec. and a Cobb value of 19.2.

EXAMPLE 3 The aspartimide obtained in Example 1 was again emulsified as described therein except that 15 grams of acetic acid were also present in the aqueous solution used for the emulsification besides the cationic emulsifier (Arquad 16/50). The surface sizing was carried out as in Example 1 to yield a paper with an ink resistance of 1.102 sec. and a Cobb value of 20.0.

EXAMPLE 4 2 mols of octadecylamine were melted together with 1 mol of maleic acid anhydride and heated at l80200C. for one-half hour. The solidified melt which consisted primarily of N,N-dioctadecylaspartimide having the formula was emulsified as in Examplel and then'made up into an aqueous sizing liquor and applied to the paper exactly as described in Example 1. In this case, a paper was obtained'with an ink resistance of 1.048 sec. and a Cobb value of. 19.2.

EXAMPLES The surface sizing-described Example 4 was carried out with the aspartimide sizing agent as described therein but using a paper which differed from Example 4 in.tha t.it contained sufficient aluminum; sulfate to yield :a pH- valueof 4,5, The sized paper exhibited an ink resistance of 2.934 sec. and aCobb valueof ":jEXAMPiLEt) .ln a paper machinetypef.Kaum uerer usedfor test ing purposes,v there was processeda neutral pulpof coniferous cellulose sulfite pulp and ,30% beech 7 EXAMPLE 7 3 mols of octadecylamine were melted together with 2 mols of maleic acid anhydride and heated for onehalf hour at a temperature of 180200C. The elemen tary analysis of the melt recrystallized from acetone identified the composition as being that of N,N-di-( N- octadecylsuccinimido)-octadecy1amine having the formula The crude melt was emulsified as in Example 1. It was then added as a sizing agent tothe pulp as in Example 6. The resulting paper had an ink resistance of 2.000 sec. and a Cobb value of 21.0.

EXAMPLE 8 1 mol of N,N-dioctadecylpropylenediaminc-1,3 was melted together with 1 mol of maleic acid anhydride at the lowest possible temperature. Into this melt, there was introduced 0.5 mols of 1.6-diaminohexane, and the mixture was then heated for one-half hour at l-200C. The resulting composition was identified by elemantary analysis as being that of N,N-bis- (dioctadecylaminopropylsuccinimido)-1.6- diaminohexane of the formula it being understood that the reaction product may also contain some N-monosubstituted compounds which also fall within the scope of the invention.

The melt of this mixture was emulsified as in Example l and was then added as a sizing agent to the pulp as in Example 6. The internally sized paper product had an ink resistance of 900 sec. and a Cobb value of 19.0.

The invention is hereby claimed as follows:

1. A stable sizing agent for paper comprising:

a. water;

b. an emulsifying agent; and

c. as the active sizing component an N,N'-alkylsubstituted aspartimide in which at least one alkyl substituent consists essentially of an alkyl chain of at least 16 up to about 40 carbon atoms.

2'. A sizing agent as claimed in claim 1 wherein said alkyl chain contains about 18 to 40 carbon atoms.

3. A sizing agent as claimed in claim 1 wherein said alkyl chain is interrupted by one to two hetero atoms selected from the group consisting of nitrogen, oxygen and sulfur.

4. A sizing agent as claimed in claim 1 wherein said alkyl chain contains from one to two functional groups selected from the class consisting of amino, hydroxy, ether, ester, carboxyl, carbonyl, thioether, thioester and sulfono groups.

5. A sizing agent as claimed in claim 1 wherein the emulsifying agent is a surface active cationic or nonionic emulsifier.

6. A sizing agent as claimed in claim 1 in further combination with a protective colloid.

7. A sizing agent as claimed in claim 1 in further combination with a degraded or cationic starch as an additional sizing component.

8. A sizing agent as claimed in claim 1 containing an inorganic or organic acid.

9. A sizing agent as claimed in claim 1 applied to a cellulosic paper product as an internal or surface sizing.

10. A method of sizing paper which comprises applying to a fibrous paper material a sizing composition containing water, an emulsifying agent and as the active sizing component an N,N'-alkyl-substituted aspartimide in which at least one alkyl substituent consists essentially of at least 16 up to about 40 carbon atoms.

1-1. A method as claimed in claim 10 wherein said sizing composition is applied at a pH-value above 4.5.

12. A method as claimed in claim 1 1 wherein said sizing composition is applied at a pH-value of about 6 to 

1. A STABLE SIZING AGENT FOR PAPER COMPRISING: A, WATER, B. AN EMULSIFYING AGENT, AND C. AS THE ACTIVE SIZING COMPONENT AN N,N'' -ALKYL-SUBSTITUTED ASPARTIMIDE IN WHICH AT LEAST ONE ALKYL SUBSTITUENT CONSISTS ESSENTIALLY OF AN ALKYL CHAIN OF AT LEAST 16 UP TO ABOUT 40 CARBON ATOMS.
 2. A sizing agent as claimed in claim 1 wherein said alkyl chain contains about 18 to 40 carbon atoms.
 3. A sizing agent as claimed in claim 1 wherein said alkyl chain is interrupted by one to two hetero atoms selected from the group consisting of nitrogen, oxygen and sulfur.
 4. A sizing agent as claimed in claim 1 wherein said alkyl chain contains from one to two functional groups selected from the class consisting of amino, hydroxy, ether, ester, carboxyl, carbonyl, thioether, thioester and sulfono groups.
 5. A sizing agent as claimed in claim 1 wherein the emulsifying agent is a surface active cationic or non-ionic emulsifier.
 6. A sizing agent as claimed in claim 1 in further combination with a protective colloid.
 7. A sizing agent as claimed in claim 1 in further combination with a degraded or cationic starch as an additional sizing component.
 8. A sizing agent as claimed in claim 1 containing an inorganic or organic acid.
 9. A sizing agent as claimed in claim 1 applied to a cellulosic paper product as an internal or surface sizing.
 10. A method of sizing paper which comprises applying to a fibrous paper material a sizing composition containing water, an emulsifying agent and as the active sizing component an N,N''-alkyl-substituted aspartimide in which at least one alkyl substituent consists essentially of at least 16 up to about 40 carbon atoms.
 11. A method as claimed in claim 10 wherein said sizing composition is applied at a pH-value above 4.5.
 12. A method as claimed in claim 11 wherein said sizing composition is applied at a pH-value of about 6 to
 9. 